Last year thr leaves on my lilac tree started curling and dying, I found tiny worms inside. How do I stop it?

I planted a lilac treey 2.5 years ago and the first year was fine, still no flowers, but last year the leaves were starting strting to show holes in most and turn brown, some were even curled up and when I opened the curled leaf up, it appeared to be some kind of very small cocoon. Is there a way to prevent this from happening again this year? Also should I be cutting back any of the branches, or just leave it be?
Last year thr leaves on my lilac tree started curling and dying, I found tiny worms inside. How do I stop it?
Spray with liquid 7 or isotox and make sure to spray the underside of the leaves as well.
Reply:spray with liquid Sevin or Malithon